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Subject: Re: [PATCH v2 2/3] fpga manager: framework core
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From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
In-Reply-To: <20141024105200.GA20775@amd>
Date: Fri, 24 Oct 2014 13:55:10 +0300
Cc: atull@opensource.altera.com,
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To: Pavel Machek <pavel@denx.de>
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Hi Pavel,

> On Oct 24, 2014, at 1:52 PM, Pavel Machek <pavel@denx.de> wrote:
> 
> Hi!
> 
>> * /sys/class/fpga_manager/<fpga>/firmware
>>  Name of FPGA image file to load using firmware class.
>>  $ echo image.rbf > /sys/class/fpga_manager/<fpga>/firmware
> 
> I .. still don't think this is good idea. What about namespaces?
> The path corresponds to path in which namespace?
> 

FWIW the overlays patchset uses binary configfs attribute to make this work.

>> +int fpga_mgr_write(struct fpga_manager *mgr, const char *buf, size_t count)
>> +{
>> +	int ret;
>> +
>> +	if (test_and_set_bit_lock(FPGA_MGR_BUSY, &mgr->flags))
>> +		return -EBUSY;
>> +
>> +	dev_info(mgr->dev, "writing buffer to %s\n", mgr->name);
>> +
>> +	ret = __fpga_mgr_write(mgr, buf, count);
>> +	clear_bit_unlock(FPGA_MGR_BUSY, &mgr->flags);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(fpga_mgr_write);
> 
> Is the EBUSY -- userspace please try again, but you don't know when to
> try again -- right interface? I mean, normally kernel would wait, so
> that userland does not have to poll?
> 
>> +static ssize_t fpga_mgr_firmware_store(struct device *dev,
>> +				       struct device_attribute *attr,
>> +				       const char *buf, size_t count)
>> +{
>> +	struct fpga_manager *mgr = dev_get_drvdata(dev);
>> +	unsigned int len;
>> +	char image_name[NAME_MAX];
>> +	int ret;
>> +
>> +	/* lose terminating \n */
>> +	strcpy(image_name, buf);
>> +	len = strlen(image_name);
>> +	if (image_name[len - 1] == '\n')
>> +		image_name[len - 1] = 0;
>> +
>> +	ret = fpga_mgr_firmware_write(mgr, image_name);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return count;
>> +}
> 
> This shows why the interface is not right... Valid filename may
> contain \n, right? It may even end with \n.
> 

I could argue that a valid firmware file is one that’s well formed and does not
contain those characters.

I guess this is only for make echo file >foo work. You could specify that echo -n file >foo is
required.


> Best regards,
> 									Pavel
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Regards

— Pantelis

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